1. Field of the Invention
The present invention relates generally to apparatus and method for separating liquids and, in particular, to apparatus and method for separating a first liquid and a second liquid from mixtures of the first liquid and second liquid employing a venturi device.
2. Discussion of the Prior Art
There can be various circumstances in which the need or preference exists for separating liquids that comprise a mixture of the liquids. Examples of such circumstances are present in a variety of industrial operations.
Many industrial operations such as grinding, milling and turning for example create heat and involve the generation of particles such as chips, shavings and fines. Liquid coolants, sometimes referred to as cutting oils, metalworking fluids or metal removing fluids, are often used in such processes to cool the working area, wash the particles away from the working area and generally facilitate the performance of the operation. The coolants also can provide lubricity for the tools performing the work and the work pieces to which the tools are applied. In addition, the coolant can provide corrosion control for the machines involved in the machining operations. In performing these functions, coolants can improve machinability, increase productivity and extend tool life.
Three classes of fluids that typically are employed as coolants include: soluble oil coolants that generally comprise an emulsion of oil and water; semi-synthetic coolants that contain both oil and a synthetic material such as a polymer; and synthetic coolants that include polymers in place of oil. Each class of these coolants has its own operational strengths and weaknesses. In any case, however, the coolants as they perform their functions can become contaminated with foreign materials which can cause the coolants to loose their effectiveness.
Examples of foreign materials that can contaminate the coolants include both solid contaminants and liquid contaminants. The solid contaminants typically comprise the chips, shavings and fines that are generated during the machining operation. The solid contaminants can provide a surface area for bacteria and fungi that foul and degrade the coolants to attach. Liquid contaminants can comprise, for example, oils that are used to lubricate components of the machine involved in the operation, such as way, slide, gear and spindle lubricants, hydraulic fluids and lubricants or other contaminants that are carried by the work piece from a previous processing operation. Such liquid contaminants generally are referred to, either individually or collectively, as tramp oils.
Typically in these industrial operations, the machining coolant is applied directly to the working area after which the coolant passes through the machine at which the machining work is being performed and is collected in a sump often located at the bottom of the machine. Typically, the coolant is pumped out of the sump and returned to the working area and in this way is constantly recirculated between the working area and the sump. As this recirculation continues, the coolant can become more and more contaminated with solid and liquid contaminants until the coolant essentially looses its effectiveness. Because the practice of discarding and replacing coolants that have become contaminated after only limited use is costly and wasteful, coolant management or maintenance programs that extend the useful life of the coolants can be implemented.
One aspect of a coolant management program can involve the separation of the solid contaminants from the coolant by settling of the solid contaminants. Settling can take place in the sump but is not particularly effective for finely divided solid particles which, if not removed from the liquid in the sump, can be returned to the working area and potentially negatively influence the operation such as by abrading important surfaces. In addition, the solid particles that settle at the bottom of the sump can provide a site for the growth of harmful bacteria particularly if the solid particles are not removed from the sump on a regular basis. Consequently, some coolant management programs make use of mechanical filters through which the coolant from the working machines is passed prior to being delivered to the sump or delivered to equipment for reconditioning the coolant by the separation of the coolant and the liquid contaminants.
As far as liquid contaminants such as tramp oils are concerned, such contaminants can degrade the coolant by, for example, destabilizing the emulsion that often forms the coolant. Because the coolant typically is heavier than the liquid contaminants and the coolant and liquid contaminants are at least somewhat immiscible with one another, separation of the liquid contaminants and the coolant can take place in the sump if a sufficient residence time for the separation to occur is provided at the sump. Thus the liquid contaminants being lighter than the coolant, will be supported or float on the coolant. To take advantage of the separation of the coolant and the liquid contaminants at the sump, the location at which coolant is withdrawn from the sump and recirculated to the working machine is located towards the bottom of the sump where substantially only the coolant is present. The floating liquid contaminants can then be removed by disk or belt skimmers or the like as part of a coolant management program.
Typically, the coolant and the liquid contaminants are not entirely immiscible or, in some cases, the coolant and the liquid contaminants will not have had sufficient time to completely separate from one another in the sump. As a consequence, the floating liquid at the top of the sump will comprise a mixture of the liquid contaminants and the coolant. In that case, it can be advantageous to recover the coolant from the mixture. This can be accomplished as part of a recycling operation by pumping the mixture to a liquid separator or coalescing apparatus where the coolant is separated from the mixture and thereafter returned to near the bottom of the sump where substantially only the coolant is present. At the same time, the liquid contaminants are removed from the separator and appropriately disposed of. In addition, rather than having the mixture of the coolant and the liquid contaminants first delivered to a sump, the coolant can be recovered by sending the mixture of coolant and liquid contaminants directly from the working machine to recycling equipment comprising a filter for removing solids and a liquid separator or coalescing apparatus at which the coolant is recovered and returned to the working machine.